/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package commons.validator.routines.checkdigit;
/**
* Modulus 11 <b>ISBN-10</b> Check Digit calculation/validation.
* <p>
* ISBN-10 Numbers are a numeric code except for the last (check) digit
* which can have a value of "X".
* <p>
* Check digit calculation is based on <i>modulus 11</i> with digits being weighted
* based by their position, from right to left with the first digit being weighted
* 1, the second 2 and so on. If the check digit is calculated as "10" it is converted
* to "X".
* <p>
* <b>N.B.</b> From 1st January 2007 the book industry will start to use a new 13 digit
* ISBN number (rather than this 10 digit ISBN number) which uses the EAN-13 / UPC
* (see {@link EAN13CheckDigit}) standard.
* <p>
* For further information see:
* <ul>
* <li><a href="http://en.wikipedia.org/wiki/ISBN">Wikipedia - International
* Standard Book Number (ISBN)</a>.</li>
* <li><a href="http://www.isbn.org/standards/home/isbn/transition.asp">ISBN-13
* Transition details</a>.</li>
* </ul>
*
* @version $Revision$
* @since Validator 1.4
*/
public final class ISBN10CheckDigit extends ModulusCheckDigit {
private static final long serialVersionUID = 8000855044504864964L;
/** Singleton ISBN-10 Check Digit instance */
public static final CheckDigit ISBN10_CHECK_DIGIT = new ISBN10CheckDigit();
/**
* Construct a modulus 11 Check Digit routine for ISBN-10.
*/
public ISBN10CheckDigit() {
super(11);
}
/**
* Calculates the <i>weighted</i> value of a charcter in the
* code at a specified position.
*
* <p>For ISBN-10 (from right to left) digits are weighted
* by their position.</p>
*
* @param charValue The numeric value of the character.
* @param leftPos The position of the character in the code, counting from left to right
* @param rightPos The positionof the character in the code, counting from right to left
* @return The weighted value of the character.
*/
protected int weightedValue(int charValue, int leftPos, int rightPos) {
return charValue * rightPos;
}
/**
* <p>Convert a character at a specified position to an
* integer value.</p>
*
* <p>Character 'X' check digit converted to 10.</p>
*
* @param character The character to convert.
* @param leftPos The position of the character in the code, counting from left to right
* @param rightPos The position of the character in the code, counting from right to left
* @return The integer value of the character.
* @throws CheckDigitException if an error occurs.
*/
protected int toInt(char character, int leftPos, int rightPos)
throws CheckDigitException {
if (rightPos == 1 && character == 'X') {
return 10;
}
return super.toInt(character, leftPos, rightPos);
}
/**
* <p>Convert an integer value to a character at a specified position.</p>
*
* <p>Value '10' for position 1 (check digit) converted to 'X'.</p>
*
* @param charValue The integer value of the character.
* @return The converted character.
* @throws CheckDigitException if an error occurs.
*/
protected String toCheckDigit(int charValue)
throws CheckDigitException {
if (charValue == 10) {
return "X";
}
return super.toCheckDigit(charValue);
}
}